LNSC-2420-Firmware/README.md

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2021-06-12 18:40:36 +02:00
# Firmware for the LNSC-2420 Solar Charger
The LNSC-2420 is a PWM-based solar charge regulator for 24 V systems supporting
up to 20 A charging current.
Noteworthy features:
- High-side switching with N-Channel MOSFETs:
- Gate voltage is provided by a charge pump which doubles the battery
voltage.
- The MOSFETs are controlled using GPIOs.
- Current and voltage measurement:
- The solar current, load current, solar voltage, battery voltage and charge
pump output voltage are measured using the internal ADC of the STM32F030.
- Low power usage:
- The charge pump is disabled if both power FETs are off.
- Additionally, the microcontroller is put into deep sleep (Stop Mode) if no
solar power is available and the battery voltage is in undervoltage
protection.
- LED status display:
- 6 LEDs show the internal charging and discharging state.
- The LEDs are controlled using Charlieplexing (i.e. only 3 GPIOs are needed)
- Protections:
- Solar panel reverse current
- Battery overvoltage
- Battery undervoltage
- Load current limit
## Calibration
The sensing hardware should be quite accurate, but some minor error always
remains. They can be compensated via the parameters in `src/calibration.h`.
To adjust those parameters, first set all `CAL_FACTOR`s to 1000, recompile and
flash the firmware. Then watch the RS485 output, which contains all
measurements in a line starting with `MEAS`. Apply a known current/voltage for
each measurement and calculate:
Actual value
CAL_FACTOR = 1000 * -----------------------
Value shown by firmware
Round to the nearest integer and replace the 1000 in `src/calibration.h` by the
calculated value.
## Customization
All customizable parameters can be adjusted in `src/config.h`.
## License
The code in this repository (except submodules) is licensed under the [MIT license](LICENSE).